I'm interested in your thoughts on the "shifting force directions and responsibilities" of "kokyu tricks" beyond, or in contrast to, the kind of exercise I described above.

Just as a rough idea of "shifting force directions and responsibilities, try this:

Take something about the weight of a half-gallon jug of milk in both your hands and hold it comfortably out in front of your chest about 12-16 inches from the chest about throat high. Notice that normally the body is sort of a "tower" and the shoulders hold the arms and then the weight/object. Now without moving too much, kind of "get under" the weight of the object so that the weight of the object is sitting directly on the legs and feet. Relax your body and feel the difference when you let the legs hold the object. You just shifted the load-bearing responsibilities by adjusting the force vectors within your body. Your "mind" arranged it.